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Abstract

The authors performed a retrospective study at their private small animal specialty referral practice, posing the question, “Does measurement of plasma lactate help predict outcome of patients with gastric dilatation–volvulus (GDV)?” The authors examined medical records from 2003 through 2007 and qualified 84 client-owned dogs for inclusion in the study. The subjects were selected based on a diagnosis of GDV, preoperative plasma lactate measurements, and surgical exploration. The predictor variables that the authors tested included an initial plasma lactate level >6.0 mmol/L, a decrease in the plasma lactate level of at least 50% within 12 hours, whether a liver biopsy was performed, and whether another veterinarian evaluated the dog before it was referred to the authors’ clinic. The authors tested whether these variables affected the following outcome variables: survival to discharge, death, and macroscopic gastric wall necrosis. The authors did not find a statistical relationship between lactate levels >6.0 mmol/L and gastric wall necrosis or decreased survival. They determined that the only predictor variable that affected outcome was a decrease in the plasma lactate level of at least 50% within 12 hours. They did find a statistical relationship between gastric wall necrosis and decreased survival. They determined that a lactate level of <4 mmol/L was specific, but not sensitive, for survival.

Commentary

GDV is a life-threatening problem frequently encountered in small animal practice. The ability of clinicians to assess patients and assign accurate prognoses is paramount. Lactate measurements have been previously reported to predict macroscopic gastric wall necrosis and survival.1 The authors thought that this was not true based on their clinical experience. (The authors are well published and have more than enough authority to speak on GDV.) The authors appear to have funded the study and did not benefit financially from the results.

The subject pool in this study is adequate for statistical analysis; however, the authors did not mention the size of the original pool from which the 84 test subjects were chosen. For example, the study does not state how many dogs with diagnosed GDV and measured lactate levels did not undergo surgery and were therefore excluded. This could have greatly affected the results by excluding dogs that were too clinically ill for surgery or including dogs that were aggressively resuscitated.

Survival to discharge is a straightforward outcome to measure; however, identification of macroscopic gastric wall necrosis can differ from clinician to clinician. The authors did identify specific, but fairly subjective, criteria to qualify macroscopic gastric wall necrosis. Shades of color can be interpreted differently, as can palpation of tissue.

The authors reported that gastric necrosis was the only variable in their study that affected survival to discharge. However, this result is somewhat skewed: of the 10 dogs that did not survive to discharge, seven were euthanized during exploratory laparotomy because of the extent of gastric necrosis. The authors acknowledged that it is impossible to tell whether these seven dogs would have survived had they not been euthanized. One dog that survived to discharge had severe, nonresectable gastric wall necrosis. Therefore, further studies are needed to determine whether severe, nonresectable gastric wall necrosis affects survival to discharge.

In their study, the authors saw a much higher incidence of patients with lactate levels of >6 mmol/L without gastric necrosis than in previously reported data.1 Therefore, the authors inferred that a lactate level of >6 mmol/L is not a good indicator of gastric necrosis. However, treatment of the subjects could have differed because it was not standardized for the authors’ and the previously reported study. The authors acknowledged this and stated that their quick, aggressive response could have decreased the number of subjects with gastric necrosis.

The authors concluded that an initial lactate level of <4 mmol/L is very specific, but not sensitive, for survival. According to the authors, this means that if a patient’s initial lactate level is not <4 mmol/L, survival should not be considered unlikely. However, if a patient has an initial lactate level of <4 mmol/L, survival can be considered likely.

The authors also found a relationship between reduction in initial lactate value of at least 50% within the first 12 hours and survival to discharge. The lactate values of the three dogs that died postoperatively failed to decrease by 50% in the first 12 hours. Of the dogs that survived, 70% had at least a 50% reduction in their lactate levels within the first 12 hours. The authors concluded that this may be a better prognostic indicator than a single initial plasma lactate value.

This article presented clinically relevant information that contradicted previously reported prognostic indicators. Lactate measurements, if interpreted appropriately, can be used as a prognostic indicator to enhance the clinical picture of pets for clinicians and clients. This can change the assessment, treatment, and outcome of patients with GDV.

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